Device for rapid voltage regulation in contact converters provided with switching coils



Dec. 23, 1958 A. BRANDT 2,856,149 VOLTAGE DEVICE FOR RAPID REG TION INCONTACT CONVERTERS PROVIDED WITH TCHING COILS Filed March 9, 1956 5Sheets-Sheet 1 Dec. 23, 1958 A. BRANDT 2,856,149

DEVICE FOR RAPID VOLTAGE REG TION IN CONTACT CONVERTERS PROVIDED WITHTCHING C OILS Filed March 9, l 5 Sheets-Sheet 2 Dec. 23, 1958 A. BRANDTR 2,866,149

DEVIcE FOR RAPID VOLTAGE REGULATION IN CONTACT CONVERTERS PROVIDED WITHSWITCHING COILS Filed March 9, 1956 3 Sheets-Sheet 5 DEVKCE FKIDR RAPIDVQZLTAGE REGULATION IN CGNTACT CGNVERTERE; PRGVIDEID WITH Sii/KTCHTNGUilllhfi Armand Brandt, Wettingen, Eiwitzeriand, assignor toAkitiengeseiischait Brown, ldoveri & Cie, Eaden, Switzerland, ajoint-stock company Application March 9, 1956, Serial No. 570,513

Claims priority, application Switzerland March 18, 1955 7 Claims. (Ell.321-43) The present invention concerns an arrangement for rapid voltageregulation in contact converters provided with switching coils.

The delivered direct voltage of the contact converter can be regulated,as known, in a simple manner by varying the duration of the connectioninterval of the contact currents. The variation of the connectioninterval is effected in known manner by varying either the directcurrent magnetization or the alternate current polarization of theswitching coils. In both cases, the intensity of the step current in thedisconnecting point is influenced together with the variation of theduration of the connection interval, which leads to difliculties withregard to the correct adjustment of the parallel circuit impulses to thecurrent step. Besides, both the duration of the connection interval andthe intensity of the step current at i the time of disconnection are, inthis arrangement, dependent on the phase position of the A.-C.polarization of the switching coils with regard to the position of thecontact switching times, so that the parallel circuit impulse mustalways be readjusted with each variation of the phase position, in viewof the current-less interruption of the contacts. The above mentioneddisadvantages are eliminated by the practicing of the principles of thepresent invention.

The invention consists in that two current-limiting coils are providedwhich are connected in parallel and polarized with direct current, andin that they are so connected by means of valves or rectifiers with thepolarization windings of the switching coils that the latter aremagnetized alternately by rectangular currents whose positive half-wavesare limited by one coil and whose negative half-waves are limited by theother coil, and in that one limiting coil has an additional windingwhich is traversed by a current proportional to the difference betweenthe actual value and the nominal value of the quantity to be regulated,so that the amplitude of one-half wave of this rectangular cur rent isso changed that the duration of the connection interval of the contactcurrents is influenced in a regulating sense, while the amplitude of thehalf-wave with the opposite polarity remains unchanged.

The limiting coils thus become by this measure regulating coils, whichmakes it possible to eiiect the regulation conssiderably faster thanwould be possible with sector regulators, for example. Besides, thearrangement does not require any moving parts or contacts, whichcircumstance is of advantage for the safety of the operation.

The invention is illustrated in detail by means of an embodiment shownin the accompanying drawings, in which:

Figs. 1 and 2 show the wiring of the arrangement; and Figs. 3 to 5 showoperating diagrams.

Fig. 1 shows a contact converter in a three-phase bridge connection. Thecontact converter transformer is designated at 1, the switching coilsfor the production of the low-current intervals at 2 and 3, and thecontacts of the converter at 4 and 5. The switching coils are eachequipped, in known manner, with a polarization winding 2355,1349Patented Dec. 23, 1958 2i and 31 respectively. The polarization windingsof the switching coils of phase and counterphase are fed in parallelover current-limiting coils 8, 9. Fig. 1 shows only the current-limitingcoils for the phase R. For each of the phases S and T there are alsoprovided two such limiting coils. Each current-limiting coil has twocores 1 and II, each of which is provided with a working winding a. Theworking windings are so connected in series that the two cores areoppositely magnetized.

As core material there is used a type of iron having a pronouncedmagnetization break, for example, nickel iron. The two cores of thecurrent-limiting coils are both wound with a D.-C. polarization windingb. The polarization windings b of all coils are connected in series, andare fed with direct current over a control resistance 18. Onecurrent-limiting coil 9 of each phase is also provided with a regulatingwinding c, which encloses both partial cores. The windings c of thesecurrent-limiting coils, acting as regulating coils 9, are connected inseries and are fed with a clifierential voltage which is proportional tothe deviation of the converter current from its nominal value. To thisend, a voltage is produced at the resistance 12 over a D.-C. convertercircuit 6, consisting of the D.-C. magnetized coil with feed transformer16, the valves or rectifier-s 7 and the smoothing reactor or choke 13,which voltage is proportional to the converter current, and is comparedwith a fixed voltage at the resistance 14. The ditlerential voltagewhich thus represents directly a measure of the deviation of the actualvalue from the nominal value or": the direct current of the converter,exists at the terminals of the coil windings 0, connected in series insuch a way that when the nominal value of the converter current isexceeded-that is, with positive differential vol agethe polarization ofthe regulating coils 9, caused by the windings b, is reduced, while itincreases when it is lower than the nominal valuethat is, with negativedifferential voltage. The working windings a of the coils and 9 areconnected over valves or rectifiers 16 with the inlets of thepolarization windings 21 and 31 respectively of the switching coils, insuch a way that after each halfwave the polarization windings of theswitching coils are communicated from one current-limiting coil to theother. This has the result that one of the half-waves is limited by thecoil 8 in the polarization winding of the switching coil and remainsunchanged in its amplitude, while the half-waves with opposite polarityare limited by the regulating coil 9 and can be varied in theiramplitude.

Fig. 3 shows the magnetization curves of the currentlimiting coils. Thetwo cores of the coils are polarized with direct current correspondingto the ampere windings AWg. The current in the working windings eiiectsan increase or" the magnetization by AW in one of the cores. Since thetwo cores have the same dimensions and the same number of turns, and thetwo hatched areas must be equal, the resulting circulation is increasedby Delta AW. With increasing AW+ and AW, Delta AW increases likewise. 1fthe current in the working windings is an alternating current, the DeltaAW pulsates between the value 0 and a maximum value with double themains frequency. To compensate the ampere windings Delta AW, thecurrent-limiting coils are provided with a feedback .winding d, which isfed over valves 11 in bridge connection from a shunt 15'.

Due to the broken magnetization curve of the currentlimiting coils, theamplitude of the alternating current in the working windings is limitedcorresponding to the value of the AWg, and'its current curve isapproximately rectangular. By varying the direct current polarization bymeans of the regulating Winding c, the

amplitude of the alternating current can be regulated in the workingwindings of the limiting coils.

The method of operation of the above described arrangement isrepresented schematically in Fig. 4.

Fig. 4a shows the course of the current i,, of a converter contact withpractically complete modulation, as well as the current i in thepolarization winding of the corresponding switching coil.

Fig. 4b shows the same with a highly readjusted direct voltage, that is,with a lower contact current i At the connection point A (Fig. 4a) theswitching coil is polarized by the amount I' In Fig. 5, which representsthe magnetization curve of the switching coil, the connection iseitected in the magnetized state P of the switching coil. Withincreasing current i the switching coil is magnetized by 1 the contactcurrent 1 up to the point P where the switching coil is in the saturatedstate. This point P corresponds to the point B in Fig. 4a. While theswitching coil shows a high inductivity in the region P P which limitsthe current to a low value (connecting step current), this inductivitydecreases in jumps with increased magnetization, and has practically nomore influence on the contact current i until the magnetization of theswitching coil, returning over the point P has reached the point P withdecreasing contact current in the point C (Fig. 4a). At this moment theswitching coil suddenly becomes inductive and limits the current to asmall value i (disconnecting step current). Since the switching coil hasbeen polarized, in this time interval, corresponding to the current ithe zero passage of the current occurs only in the point P'S (Fig. 5),corresponding to the point D in Fig. 4a. In the intervals AB and CD theentire current reversal voltage of the converter is therefore above theswitching coil (hatched areas); in the interval BC, however, the voltageabove the coil is very low. If the amplitude of the polarization i ofthe switching coil is reduced by the regulating coil 9 in the connectingpoint of the converter contact, the duration of the connection stepincreases according to Fig. 4b; the direct voltage delivered by theconverter diminishes and correspondingly also the direct current of theconverter. This reverse regulation of the direct current occurs, forexample, if the actual value tapped over the voltage divider 112 exceedsthe nominal value for the direct current of the converter to beregulated, which is tapped at the voltage divider 114, so that thewinding of the regulating coil reduces the action of the po larizationwinding b. But if the actual value drops below the nominal value, thepolarization of the regulating coil 9 is increased by the AW of theregulating winding 0, so that the amplitude of the polarization currentof the switching coil is also increased. Thus the duration of theconnecting step decreases, the direct voltage increases and the directcurrent is adjusted to the nominal value. Since the polarization currentis limited during the disconnecting step by the coil 8, the amount ofthe step current Delta 1 remains unchanged, because the point is fixedin Fig. 5.

The above described device regulates the direct voltage delivered by theconverter in such a way that the delivered direct current remainsconstant within certain limits, as it is desired, for example, inelectrolytic plants. But the device can also be so designed that thevoltage is regulated to a constant value. in this case, the voltages atthe resistance 14 would be compared directly with the direct voltagedelivered by the converter.

Fig. 2 shows another embodiment where the direct current convertercircuit is connected directly to the regulating winding 0 of theregulating coils so that the comparison between actual and nominalvalues can be made in the regulating coil itself.

I claim:

1. Device for rapid voltage regulation in contact converters providedwith switching coils, the switching coils of each phase of the converterhaving two current-limiting coils which are connected in parallel andpolarized with direct current, said current-limiting coils having coresof a magnetic material with a pronounced magnetization break and beingconnected to their associated switching coils by valve means so that theswitching coils are magnetized alternately by square-wave currents whosepositive half-waves are limited by one coil and whose negativehalf-waves are limited by-the other coil; means for varying theamplitude of one-half of the rectangular currents so that the durationof the connection intervals of the contact current is influenced in aregulating sense while the amplitude of the half-wave of oppositepolarity remains unchanged comprising an additional winding on one ofthe current-limiting coils which is traversed by a current proportionalto the difference between the actual and the nominal value of thequantity to be regulated.

2. Arrangement according to claim 1, characterized in that each of thecurrent-limiting coils is provided with two cores of an iron having apronounced magnetization break.

3. Arrangement according to claim 2, characterized in that each of thetwo cores has a working winding which is so connected in series that thetwo cores are oppositely magnetized, and in that a polarization windingis provided which embraces both cores.

4. Arrangement according to'claim 3, characterized in that the two coreshave an additional feed-back winding which embraces both cores and whichis fed over valves with a pulsating direct current of double mainsfrequency, proportional to the alternating current in the workingwindings.

5. Arrangement according to claim 1, characterized in that the variationof the amplitude of one half-wave of the rectangular current is effectedin dependence on the diflerence between the actual value and the nominalvalue of the direct current delivered by the contact converter;

6. Arrangement according to claim 1, characterized in that the variationof the amplitude of the half-wave of the rectangular current is effectedin dependence on the difference between the actual value and the nominalvalue of the direct voltage delivered by the contact converter.

7. A device for rapid voltage regulation of a contact converter providedwith switching coils comprising a pair of current-limiting coilsassociated with each phase of the contact converter, saidcurrent-limiting coils having cores of a material with a pronouncedmagnetic break, a source of electrical power causing saidcurrent-limiting coils to produce rectangular half-wave voltages, anauxiliary coil positioned about the core of one of said current-limitingcoils, means for producing a current proportional to the diiferencebetween the actual and the nominal value of the quantity to beregulated, said auxiliary coil being connected to said current producingmeans so that the magnetization component produced in the core willaffect the magnitude of the voltage produced by the associatedcurrent-limiting coil, and valve means connecting the current-limitingcoils to the switching coils so that the switching coils are magnetizedalternately by square wave currents whose positive half-waves arelimited by one coil and whose negative half-waves are limited by theother coil.

References Cited in the file of this patent UNl-TED STATES PATENTS2,568,140 Belamin Sept. 18, 1951 2,756,381 Rolf July 24, 1956 FOREIGNPATENTS 113,439 Sweden Mar. 13, 1945

